Singulation is the process of cutting individual dies from their lead frames on a substrate containing a number of dies. When cutting a substrate at a high speed, the resulting friction and resulting heating of the substrate is an obstacle to high speed singulation. Excessive heat from singulation can damage the die electronics and render the die electronics inoperative. Thus, coolant is used to cool and lubricate the cutting blade and substrate during singulation. FIG. 1 illustrates a prior art system 100 for cooling a saw blade 151 during singulation. The prior art cooling system 100 includes a mixing system 110, a chemical tank 120, a cooling coil 130, a pre-mixing filter 140, post mixing filter 145 and a coolant delivery means 155.
The mixing system 110 is filled with deionized water from a deionized water source 125 and a chemical from the chemical tank 120. The deionized water and the chemical are mixed in the mixing tank. This coolant within the mixing tank chamber 111 is chilled by the cooling coil 130. The fluid in the mixing chamber 111 is pumped though a filter 145 and an coolant delivery means 155 delivers the coolant onto the saw blade 151 while singulating the dies from the substrate 152. The used coolant is captured by a pan 157 for return to the mixing tank 110. This used coolant contains substrate particles from the singulation process. The larger particles are filtered out by a filter 140, such as a 100 micron filter. However, smaller particles enter the mixing system 110 and accumulate to form a sludge in the bottom of the mixing tank chamber 111.
Eventually, the cooling system 100 and singulation saw 150 has to be stopped to clean the sludge from the mixing tank chamber 111 or to clean or replace the filters 140 and 145. This stoppage causes a loss of the singulation tool productivity and the removal of the sludge causes a loss of coolant. Further, the prior art system 100 is prone to the formation of bubbles which can travel into the cooling line from the mixing and recirculation of the used coolant. These bubbles will cause gaps in the delivery of coolant to the saw blade 151 which can cause sudden heating of the sawblade 151 and thus potentially damage the electronic components being singulated. A further disadvantage of the prior art system 100 is that the system is designed for a single saw which increases the space utilization for each singulation system.
What is needed is a cooling system that has less coolant loss, requires less cleaning due to sludge buildup, does not introduce bubbles into the coolant stream, and can provide coolant to more than one singulation saw, and can continue to operate while cleaning the filters and tanks.